Advances in navigation assistance technology, which helps individuals get from one place to another, have made its use widespread. Automobiles, mobile phones, and even wrist watches either come equipped with functionality that assists with navigation or can easily be configured to have it by a user. These navigation assistance technologies allow users to plan trips and even provide substantially-real time updates regarding a user's location along a planned route. Further still, when a user takes a wrong turn (e.g., while driving), today's navigation assistance technologies are capable of recalculating a route using a new location of the user, which results from the wrong turn. These technologies are even capable of assisting users to plan routes for trips where users have limited control over operation of the vehicles they ride, such as transit-based routes where the user's movement is limited by the transit vehicles he or she is onboard (e.g., routes involving buses, subways, trains, and so on). However, the approaches used by existing navigation assistance technologies are not optimized to deal efficiently with changing such a route while a user is mid-travel. This is because, typically, navigation technologies assume that a constrained-transportation user, asking for directions, is stationary—using the user's latitude and longitude at the time a route is requested to calculate directions. In the case of transit use, this can result in directions that instruct users to walk to stops that are not in a direction their current transit vehicles are heading, or instruct users to walk to transit stops that are not nearby next stops of the transit vehicles they are currently riding.
Consequently, users may become frustrated with navigation assistance technologies when trying to use them for transportation over which their control is limited. This may cause users to forgo the use of navigation assistance technologies while traveling on vehicles that follow designated routes and a schedule of predetermined stops. Instead, users may rely on their own knowledge of transit systems or may depart such a vehicle at a next stop, and then figure out directions to a desired destination. By simply departing the vehicle at a next stop, however, a user may not be taking an optimized route (e.g., fastest, shortest, cheapest, fewest transfers, and so on) to the desired destination.